1. Field of the Invention
This invention relates to the preparation of a sustained release delivery system, and more particularly to a system using a polymer matrix containing a drug. The system is designed to administer effective levels of drugs over a sustained period of time when administered intramuscularly, epidurally or subcutaneously for the treatment of various disease states conditions. A particularly advantageous use of the system is the administration of a local anesthetic along the sheath of a nerve or muscle tissue to alleviate or ameliorate the effects of pain.
2. Description of the Prior Art
Medications have been formulated to enable the administration of drugs to occur over a wide variety of paths, including instantaneous delivery by use of injectables, and sustained, controlled and extended release delivery by use of tablets, capsules, and particulate forms which enable release of the drug to be controlled by various means, such as by resistance of the structure's coating or composition against diffusion of the drug therethrough. These systems have all found wide applications for the delivery of drugs.
None of the known drug delivery systems, however, are able to administer effective therapeutic amounts of a drug for sustained periods of time, that is, longer than 24 to 48 hours. Actually, most delivery systems maintain effective dosages for from several hours to daily doses before requiring readministration. Such systems have not been found to be effective for the long term administration of drugs that require repetitive and continued use, except of course for selected patch treatments. Drugs that have been repeatedly administered for long term treatments include but are not limited to anesthetics for treating pain, steroids and hormone administration for maintenance, modification or alteration of body chemistry, metabolism and hormone balance and regulation, vitamin and mineral supplementation, and so forth. A delivery system is therefore needed which would permit the administration of therapeutically effective amounts of drugs to enable a continued and sustained release for at least 24 hours to several days.